The sentencing judge branded her a cunning fantasist whose "tortured and perverted mind" invented a mystery stalker and rapist. But relatives, friends and anti-rape campaigners insisted on a very different picture of Gail Sherwood, a 52-year-old former childminder and mother of three daughters, as she began a two-year jail sentence for perverting the course of justice.

They say that Sherwood, from Stroud, in Gloucestershire, is the victim of a violent stalker who twice kidnapped and raped her ‑ and of a system that has badly let her down. Sherwood, 52, was convicted on Thursday after an extraordinary and deeply unsettling six-week trial, during which she insisted she had been the victim of an intense stalking campaign by an unknown attacker, culminating in the two attacks. The prosecution argued, in the end successfully, that she had made the whole story up.

Speaking to the Guardian before her sentencing, Sherwood insisted on her innocence and claimed that the police turned their attention to her after first making mistakes during the investigation into the rapes. The police, she said, were sceptical from the start. "From the beginning they never believed me," she said. "If you're a single woman on your own they think you are a fantasist. All I've ever done is tell the truth. I've never lied to anybody and this is what you get for it."

Sherwood's supporters say her conviction will discourage rape victims from reporting attacks, and maintain that a dangerous man is on the loose in Gloucestershire, who may be encouraged to strike again. The campaign group Women Against Rape (War), which is leading the fight to clear Sherwood's name, appealed for women who had been raped in the county to come forward.

The saga, described by the judge Julian Lambert as "unique", began in 2001, Sherwood claimed, when she began to be contacted and harassed by a man she did not know. "I didn't know where he came from and I still don't. I don't recognise him. He's never given me any indication as to where he knew me from."

She had not called the police. "People said: 'Don't phone them, they never believe women on their own.'"

The stalking stopped, Sherwood said, but started again in 2008. On one occasion, she told the court, she had been seized at a beauty spot near her home where she was walking her dog, raped and left tied to a fence. A few weeks later, she said, she was kidnapped from her home, knocked unconscious and driven to a local stately home where she was again raped and tied up.

The jury did not believe her story, and the sentencing judge, describing her as "cunning and highly deceitful", said she had invented a "malicious fantasy world". War argues her case was mishandled by investigators, and that there is a worrying trend among police to target rape victims after botching investigations into their complaints.

Privately Gloucestershire police concede mistakes were made. Perhaps most crucially, after the first alleged rape, Sherwood said she began carrying a penknife and that she almost certainly cut the attacker during the second attack. The knife was visible in police photographs of the scene and was picked up by a scenes of crimes officer, but was later lost.

By the time of the second alleged attack, however, officers had become convinced Sherwood was not telling the truth. They set up covert cameras and later argued in court that footage recorded by one of their cameras showed Sherwood driving off alone in her own car at the time she had alleged she had been raped in the second assault. Sherwood's supporters pointed out that a second, unidentified figure was also captured by the camera shortly beforehand.

During her trial, which cost £100,000, Sherwood spent 20 hours in the witness box defending herself against accusations of being a liar, a drunkard and a bad mother. She said the ordeal was worse than the alleged rapes.

There was shock among Sherwood's many friends and supporters when she was convicted, with around 60 people signing a letter to the judge calling the conviction "a total miscarriage of justice". It added: "We are also very concerned that as a result of this turn of events a stalker and rapist remains at large."

Campaigners point out that the clear-up rate for allegations of rape in Gloucestershire has been poor in the past and is now only just above the national average of 6.5%. At the end of last year the Gloucestershire rape crisis centre asked for more volunteers after seeing an increase of more than one-third in the number of people needing its help. Research carried out for the Home Office has suggested the police overestimate the number of false allegations made.

Detective Chief Inspector Paul Shorrock, the senior investigating officer, said the police and Crown Prosecution Service had considered very carefully before investigating Sherwood. He said they had ploughed many resources into hunting the supposed rapist before concluding he did not exist. He said one reason why they felt it necessary to pursue Sherwood was to reassure other people living nearby that there was no stalker on the loose.

The police have not been able to say what Sherwood's motive was but he said officers were convinced there was no attacker. He said the police had taken her claims seriously and investigated all allegations with care and sensitivity.

The district crown prosecutor, Rachael Scott, said: "We will continue to bring prosecutions for attempting to pervert the course of justice in cases of false allegations of rape. Genuine rape victims need to know that we take their complaints extremely seriously and every attempt will be made to reveal evidence to support them. This case was not only brought to protect the integrity of rape victims but also to demonstrate the devastating effects false allegations can have."

Sherwood's family and friends say they will stand by her. Her partner, Graham Kimber, said: "He's still out there, watching us. This place has been under siege. You may think we're mad but it's true. There's no end to it. I suspect someone round here is going through the same thing as we are."